11.basis law.

The standard units of measurement for electrical current, voltage, and resistance: 

Ohms Law: the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. . Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate:

E=IR


Ohm's Law is a very simple and useful method for analyzing electric circuits. It is used so often in the study of electricity and electronics that it needs to be committed to memory by the serious student.there's a trick to remembering how to solve for any one quantity, given the other two. First, arrange the letters E, I, and R in a triangle like this:

 




If you know E and I, and wish to determine R, just eliminate R from the picture and see what's left:











If you know E and R, and wish to determine I, eliminate I and see what's left:
 

Lastly, if you know I and R, and wish to determine E, eliminate E and see what's left:


 

Analysis of ohm’s law: Ohm's Law also makes intuitive sense if you apply it to the water-and-pipe analogy. If we have a water pump that exerts pressure (voltage) to push water around a "circuit" (current) through a restriction (resistance), we can model how the three variables interrelate. 

If the resistance to water flow stays the same and the pump pressure increases, the flow rate must also increase.

 

If the pressure stays the same and the resistance increases (making it more difficult for the water to flow), then the flow rate must decrease: 

 

If the flow rate were to stay the same while the resistance to flow decreased, the required pressure from the pump would necessarily decrease: